The pharmaceutical industry has in the last few years arrived at increasingly more effective active substances due to intensive research. Whereas most active substances developed in previous years were dosed in the multiple milligram range (conventional doses of about 20 to 150 mg per tablet), since then active substances have been invented whose dose per tablet is only about a few milligrams. Such active substances present difficulties in processing since the quantity of active substance becomes disproportionately small in relation to the remaining mass of the molding, i.e., the carrier. Consequently, sufficiently homogeneous distribution of the active substance in the entire molding cannot be readily obtained by mixing. For example, in an investigation of digoxin tablets to be found on the United States market, deviations of up to .+-.50% from the declared quantity of digoxin per tablet were established.
The active substance has hitherto had to be distributed homogeneously in the granulate, and during such distribution of low-dosage active substances, comprehensive safety precautions have been required, for example, to protect the operating personnel. Furthermore, comprehensive industrial operations such as mixing, granulation, trituration, or fine grinding have been unavoidably necessary. Moreover, in pressing tablets of low-dosage active substances, the dissolution rate and consequently the resorption capacity of the active substance in the body are influenced in a negative way by unavoidable sintering actions. In the preparation of tablets or coated-tablet cores with active substances of very low dosage, the exact dosing of these active substances is of special importance; however, this exact dosing requirement is often possible only to an insufficient degree with conventional processes.